This invention relates in general to a method and apparatus for measurement of blood flow and more particularly to the measurement of blood flow with an implantable device, especially suitable for use in conjunction with both micro- and macrosurgical procedures.
The principle of reconstructive vascular surgery is to provide and maintain blood flow to tissues and organs. With circulatory interruption distal tissues become ischemic. Over time this ischemia progresses from a reversible form (one in which restoration of blood flow re-establishes tissue viability) to an irreversible form (one in which there is cell death and irrevocable tissue damage).
Of prime importance is the monitoring of the patients, specifically the area which has been vascularized, so that if there is circulatory embarrassment it is discovered during the period of reversible ischemia. With early intervention and correction, tissue viability is restored and preserved.
Various techniques have been employed in the past for measuring blood flow in large and small blood vessels. These have included direct observation (blanche and refill technique) in tissues with a cutaneous component; Doppler and ultra sound monitors; transcutaneous oxygen probes; laser optic monitors; tracer scans; arteriography; and electromagnetic flow meters. All of these methods are limited in that they are either episodic in their monitoring, risky in their application, or not entirely reliable in their interpretation.
What is needed is a monitor that can be placed under direct vision next to a vessel and which would give continuous, reliable information regarding blood flow through that vessel; and one which would warn of any flow abnormalities. When no longer needed, the monitor should have the ability to be removed atraumatically and transcutaneously. Its use should be valid in all types of vascular surgery (microsurgical, macrosurgical) and in all types of repairs (arteries, veins, vein grafts, prosthetic grafts). Uses may also include monitoring organ function, for example for diagnosis.